Comstock/Thinkstock(LOS ANGELES) -- Police in Southern California say they suspect that a fired cop is connected to the shootings -- one fatal -- of three police officers Thursday morning, as well as the weekend slayings of an assistant women's college basketball coach and her fiancé in what cops believe are acts of revenge against the LAPD, as suggested in the suspect's online manifesto.

Former police officer Christopher Jordan Dorner, 33, has been publically named as a suspect in the killings of Monica Quan, 28, and her 27-year-old fiancé, Keith Lawrence, Irvine police Chief David L. Maggard said at a news conference Wednesday night.

"We are considering him armed and dangerous," Lt. Julia Engen of the Irvine Police Department said.

Police say Dorner shot at four officers in two incidents overnight, hitting three of them: one in Corona, Calif., and two in Riverside, Calif.

Sgt. Rudy Lopez of the LAPD said two LAPD officers were in Corona and were heading out on special detail to check on one of the individuals named in Dorner's manifesto. Dorner allegedly grazed one of them but missed the other.

The Riverside Police Department said two of its officers were shot before one of them died, ABC News affiliate KABC-TV reported. The extent of the other's injuries is unclear.

Police suspected a connection to Dorner.

"They were on routine patrol stopped at a stop light when they were ambushed," Lt. Guy Toussant of the Riverside police department said.

Police around Southern California are wearing tactical gear, including helmets and guns across their chests. The light-up signs along California highways show the license plate number of Dorner's car, and say to call 911 if it is seen. The problem, police say, is that they believe Dorner is switching license plates on his car, a 2005 charcoal gray Nissan Titan pickup truck.

Lawrence was found slumped behind the wheel of his white Kia in the parking lot of their upscale apartment complex on Sunday and Quan was in the passenger seat.

"Of particular interest at this point in the investigation is a multi-page manifesto in which the suspect has implicated himself in the slayings," Maggard said.

Police said Dorner's manifesto included threats against members of the LAPD. Police say they are taking extra measures to ensure the safety of officers and their families.

The document, allegedly posted on an Internet message board this week, blames Quan's father, retired LAPD Capt. Randy Quan, for his firing from the department in 2008.

One passage from the manifesto reads, "I will bring unconventional and asymmetrical warfare to those in LAPD uniform whether on or off duty."

"I never had the opportunity to have a family of my own," Dorner allegedly writes. "I'm terminating yours."